Magneto-optical circulator is a key device for reducing the optical signal crosstalk and improving the component integration in integrated optics. The magneto-optical circulator can realize circular transmission of optical signals in single rotational direction among channels by utilizing the non-reciprocal characteristic of magneto-optical materials, so as to achieve the aims of preventing the signal reflection, eliminating the signal crosstalk and guaranteeing the normal operation of an optical circuit system, thereby being an indispensable performance-optimization component in an integrated optical system.
Currently, the use of photonic crystal all-optical logic elements to obtain a complex optical circuit with different functions is a popular study. For example, the use of “AND”, “OR,” “NOT”, “XOR” and other photonic crystal basic logic functional elements to construct photonic crystal half adders, photonic crystal comparators, and photonic crystal A/D (D/A) converters. The research of photonic crystal logic integrated optical circuits has potential application value to the development of a new generation of optical integrated chips. However, with the increase of the integration scale in the photonic crystal integrated optical circuits, the optical signal interference among components is greatly increased and the optical circuits even cannot realize their normal logic functions under severe cases. Therefore, the development of corresponding magneto-optical circulators has become a key technical problem to be solved for improving the stability of signal transmission inside photonic crystal integrated optical circuits and guaranteeing the normal operation of the optical circuit system.
By now, the available photonic crystal logic elements are basically realized in an air-substrate-dielectric-column structure (square lattice arrangement), while the several available photonic crystal circulators are basically realized in a dielectric-substrate-air-column structure (hexagonal lattice arrangement), [the TE band gap of the air-substrate-dielectric-column structure is deeper, compared with that of the dielectric-substrate-air-column structure, (the advantages of deeper band gap are that the required dimension of a photonic crystal is smaller under the same performance index, so that the integration scale can be easily improved), so that the air-substrate-dielectric-column structure has the advantages of avoiding the interference of TM mode, having excellent working characteristics and simple structural form, and being easy to design and produce], so that the application scope thereof has certain limitation. Therefore, as for the research of photonic crystal magneto-optical circulators and particularly the research of photonic crystal magneto-optical circulators with the air-substrate-dielectric-column structure (square lattice arrangement) which are matched with the available photonic crystal logic elements, further development is required in the aspects of structure type, functional application and so on.
The photonic crystal magneto-optical circulator has important application value for the large-scale integration of the photonic crystal logic elements, is helpful to eliminate the effects of signal crosstalk and light beam reflection, is favorable to promote the functional match of various components in an optical circuit, and is an indispensable anti-interference component in the integrated optical system.